Conventionally, a train-of-vehicle travel support device has been known, in which a magnetic marker is embedded in the center of a running road of a vehicle, a magnetic sensor of vehicle detects the magnetism of the magnetic marker to specify road surface lateral displacement of the vehicle, and automatic steering of the vehicle is carried out along the magnetic marker, thereby controlling a train-of-vehicle travel of a plurality of vehicles. In the train-of-vehicle travel support device, by sending/receiving data such as a vehicle identifying number and the velocity, etc. through the radio communication or the optical communication between a preceding vehicle and a following vehicle, it is possible to carry out automatic velocity control of the following vehicle which follows the preceding vehicle and automatic braking control (for example, refer to Patent Literature 1).